1. Field of the Invention
The present invention relates to a hydraulic drive device that drives a hydraulic pump and a hydraulic motor utilizing an electric motor as a direct drive source.
2. Description of the Related Art
A gasoline engine or the like has been conventionally used to drive a hydraulic pump or a hydraulic motor and operate a hydraulic shovel, a bulldozer or the like. However, no technique has been proposed to directly connect a rotational output of an electric motor to a hydraulic pump or a hydraulic motor and drive the mentioned hydraulic pump or hydraulic motor as a drive source of a hydraulic drive machine such as hydraulic shovel or bulldozer. This is because it has been considered that output of the electric motor is not high enough to be used as a direct drive source power for driving the hydraulic pump or the hydraulic motor and is deficient to operate the hydraulic drive machine such as hydraulic shovel or bulldozer.